[tzs]

Here in Western Washington, I've not seen any site mixing vaccines. One Walgreens might have Moderna and another Pfizer, but any given day any particular store will only have one of them.

Most places say when you sign up which they will have for your appointment, but if they do not you can often tell by looking at the eligibility. If they are offering appointments to people age 16+, they are using Pfizer. If 18+, Moderna.

Most places here also tell you on the signup form that your second appointment will be the same time and place exactly N weeks after the first. If N = 3, they are using Pfizer. If N = 4, Moderna.